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4. Formal Logic / D. Modal Logic ML / 6. Temporal Logic

[Inferences across past, present and future]

4 ideas
It is important that the quantification over temporal entities is timeless [Quine]
     Full Idea: It would be hard to exaggerate the importance of recognising the timelessness of quantification over temporal entities.
     From: Willard Quine (Mr Strawson on Logical Theory [1953], IV)
     A reaction: 'Some moments in this cricket match were crucial'. The domain is not timeless, but consists of moments in this match. Can you say the quantifier is timeless but its domain is not? Only in the sense that 'very' is a timeless word, I think.
With four tense operators, all complex tenses reduce to fourteen basic cases [Burgess]
     Full Idea: Fand P as 'will' and 'was', G as 'always going to be', H as 'always has been', all tenses reduce to 14 cases: the past series, each implying the next, FH,H,PH,HP,P,GP, and the future series PG,G,FG,GF,F,HF, plus GH=HG implying all, FP=PF which all imply.
     From: John P. Burgess (Philosophical Logic [2009], 2.8)
     A reaction: I have tried to translate the fourteen into English, but am not quite confident enough to publish them here. I leave it as an exercise for the reader.
F: will sometime, P: was sometime, G: will always, H: was always [Fitting/Mendelsohn]
     Full Idea: We introduce four future and past tense operators: FP: it will sometime be the case that P. PP: it was sometime the case that P. GP: it will always be the case that P. HP: it has always been the case that P. (P itself is untensed).
     From: M Fitting/R Mendelsohn (First-Order Modal Logic [1998], 1.10)
     A reaction: Temporal logic begins with A.N. Prior, and starts with □ as 'always', and ◊ as 'sometimes', but then adds these past and future divisions. Two different logics emerge, taking □ and ◊ as either past or as future.
We can treat modal worlds as different times [Sider]
     Full Idea: We can think of the worlds of modal logic as being times, rather than 'possible' worlds.
     From: Theodore Sider (Logic for Philosophy [2010], 7.3.3)